❶ 求一篇關於基於單片機的超聲波測距儀設計的英文資料（附中文翻譯更美，呵呵），畢業設計用。謝謝
This article described the three directions (before, left, right) ultrasonic ranging system is to understand the front of the robot, left and right environment to provide a movement away from the information. (Similar to GPS Positioning System)
A principle of ultrasonic distance measurement
1, the principle of piezoelectric ultrasonic generator
Piezoelectric ultrasonic generator is the use of piezoelectric crystal resonators to work. Ultrasonic generator, the internal structure as shown in Figure 1, it has two piezoelectric chip and a resonance plate. When it's two plus pulse signal, the frequency equal to the intrinsic piezoelectric oscillation frequency chip, the chip will happen piezoelectric resonance, and promote the development of plate vibration resonance, ultrasound is generated. Conversely, if the two are not inter-electrode voltage, when the board received ultrasonic resonance, it will be for vibration suppression of piezoelectric chip, the mechanical energy is converted to electrical signals, then it becomes the ultrasonic receiver.
2, the principle of ultrasonic distance measurement
Ultrasonic transmitter in a direction to launch ultrasound, in the moment to launch the beginning of time at the same time, the spread of ultrasound in the air, obstacles on his way to return immediately, the ultrasonic reflected wave received by the receiver immediately stop the clock. Ultrasound in the air as the propagation velocity of 340m / s, according to the timer records the time t, we can calculate the distance between the launch distance barrier (s), that is: s = 340t / 2
Ultrasonic Ranging System for the Second Circuit Design
System is characterized by single-chip microcomputer to control the use of ultrasonic transmitter and ultrasonic receiver since the launch from time to time, single-chip selection of 8751, economic-to-use, and the chip has 4K of ROM, to facilitate programming. Circuit schematic diagram shown in Figure 2. Draw only the front range of the circuit wiring diagram, left and right in front of Ranging Ranging circuits and the same circuit, it is omitted.
1,40 kHz ultrasonic pulse generated with the launch
Ranging system using the ultrasonic sensor of piezoelectric ceramic sensors UCM40, its operating voltage of the pulse signal is 40kHz, which by the single-chip implementation of the following proceres to generate.
puzel: mov 14h, # 12h; ultrasonic firing continued 200ms
here: cpl p1.0; output 40kHz square wave
nop;
nop;
nop;
djnz 14h, here;
ret
Ranging in front of single-chip termination circuit P1.0 input port, single chip implementation of the above procere, the P1.0 port in a 40kHz pulse output signal, after amplification transistor T, the drive to launch the first ultrasonic UCM40T, issued 40kHz ultrasonic pulse, and the continued launch of 200ms. Ranging the right and the left side of the circuit, respectively, then input port P1.1 and P1.2, the working principle and circuit in front of the same location.
2, reception and processing of ultrasonic
Used to receive the first launch of the first pair UCM40R, the ultrasonic pulse molation signal into an alternating voltage, the op-amp amplification IC1A and after polarization IC1B to IC2. IC2 is locked loop with audio decoder chip LM567, internal voltage-controlled oscillator center frequency of f0 = 1/1.1R8C3, capacitor C4 determine their target bandwidth. R8-conditioning in the launch of the carrier frequency on the LM567 input signal is greater than 25mV, the output from the high jump 8 feet into a low-level, as interrupt request signals to the single-chip processing.
Ranging in front of single-chip termination circuit output port INT0 interrupt the highest priority, right or left location of the output circuit with output gate IC3A access INT1 port single-chip, while single-chip P1.3 and P1. 4 received input IC3A, interrupted by the process to identify the source of inquiry to deal with, interrupt priority level for the first left right after. Part of the source code is as follows:
receive1: push psw
push acc
clr ex1; related external interrupt 1
jnb p1.1, right; P1.1 pin to 0, ranging from right to interrupt service routine circuit
jnb p1.2, left; P1.2 pin to 0, to the left ranging circuit interrupt service routine
return: SETB EX1; open external interrupt 1
pop? acc
pop? psw
reti
right: ...?; right location entrance circuit interrupt service routine
? Ajmp? Return
left: ...; left Ranging entrance circuit interrupt service routine
? Ajmp? Return
4, the calculation of ultrasonic propagation time
When you start firing at the same time start the single-chip circuitry within the timer T0, the use of timer counting function records the time and the launch of ultrasonic reflected wave received time. When you receive the ultrasonic reflected wave, the receiver circuit outputs a negative jump in the end of INT0 or INT1 interrupt request generates a signal, single-chip microcomputer in response to external interrupt request, the implementation of the external interrupt service subroutine, read the time difference, calculating the distance . Some of its source code is as follows:
RECEIVE0: PUSH PSW
PUSH ACC
CLR EX0; related external interrupt 0
? MOV R7, TH0; read the time value
MOV R6, TL0?
CLR C
MOV A, R6
SUBB A, # 0BBH; calculate the time difference
MOV 31H, A; storage results
MOV A, R7
SUBB A, # 3CH
MOV 30H, A?
SETB EX0; open external interrupt 0
POP ACC?
POP PSW
RETI
Fourth, the ultrasonic ranging system software design
Software is divided into two parts, the main program and interrupt service routine, shown in Figure 3 (a) (b) (c) below. Completion of the work of the main program is initialized, each sequence of ultrasonic transmitting and receiving control.
Interrupt service routines from time to time to complete three of the rotation direction of ultrasonic launch, the main external interrupt service subroutine to read the value of completion time, distance calculation, the results of the output and so on.
V. CONCLUSIONS
Required measuring range of 30cm ~ 200cm objects inside the plane to do a number of measurements found that the maximum error is 0.5cm, and good reprocibility. Single-chip design can be seen on the ultrasonic ranging system has a hardware structure is simple, reliable, small features such as measurement error. Therefore, it can be used not only for mobile robot can be used in other detection systems.
Thoughts: As for why the receiver do not have the transistor amplifier circuit, because the magnification well, CX20106 integrated amplifier, but also with automatic gain control level, magnification to 76dB, the center frequency is 38k to 40k, is exactly resonant ultrasonic sensors frequency
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本文所介紹的三方向（前、左、右）超聲波測距系統，就是為機器人了解其前方、左側和右側的環境而提供一個運動距離信息。（類似GPS定位系統）
一 超聲波測距原理
1、壓電式超聲波發生器原理
壓電式超聲波發生器實際上是利用壓電晶體的諧振來工作的。超聲波發生器內部結構如圖1所示，它有兩個壓電晶片和一個共振板。當它的兩極外加脈沖信號，其頻率等於壓電晶片的固有振盪頻率時，壓電晶片將會發生共振，並帶動共振板振動，便產生超聲波。反之，如果兩電極間未外加電壓，當共振板接收到超聲波 時，將壓迫壓電晶片作振動，將機械能轉換為電信號，這時它就成為超聲波接收器了。
2、超聲波測距原理
超聲波發射器向某一方向發射超聲波，在發射時刻的同時開始計時，超聲波在空氣中傳播，途中碰到障礙物就立即返回來，超聲波接收器收到反射波就立即停止計時。超聲波在空氣中的傳播速度為340m/s，根據計時器記錄的時間t，就可以計算出發射點距障礙物的距離(s)，即：s=340t/2
二 超聲波測距系統的電路設計
系統的特點是利用單片機控制超聲波的發射和對超聲波自發射至接收往返時間的計時，單片機選用8751，經濟易用，且片內有4K的ROM，便於編程。電路原理圖如圖2所示。其中只畫出前方測距電路的接線圖，左側和右側測距電路與前方測距電路相同，故省略之。
1、40kHz 脈沖的產生與超聲波發射
測距系統中的超聲波感測器採用UCM40的壓電陶瓷感測器，它的工作電壓是40kHz的脈沖信號，這由單片機執行下面程序來產生。
puzel： mov 14h, #12h；超聲波發射持續200ms
here： cpl p1.0 ； 輸出40kHz方波
nop ；
nop ；
nop ；
djnz 14h，here；
ret
前方測距電路的輸入端接單片機P1.0埠，單片機執行上面的程序後，在P1.0 埠輸出一個40kHz的脈沖信號，經過三極體T放大，驅動超聲波發射頭UCM40T，發出40kHz的脈沖超聲波，且持續發射200ms。右側和左側測 距電路的輸入端分別接P1.1和P1.2埠，工作原理與前方測距電路相同。
2、超聲波的接收與處理
接收頭採用與發射頭配對的UCM40R，將超聲波調制脈沖變為交變電壓信號，經運算放大器IC1A和IC1B兩極放大後加至IC2。IC2是帶有鎖 定環的音頻解碼集成塊LM567，內部的壓控振盪器的中心頻率f0=1/1.1R8C3，電容C4決定其鎖定帶寬。調節R8在發射的載頻上，則LM567 輸入信號大於25mV，輸出端8腳由高電平躍變為低電平，作為中斷請求信號，送至單片機處理.
前方測距電路的輸出端接單片機INT0埠，中斷優先順序最高，左、右測距電路的輸出通過與門IC3A的輸出接單片機INT1埠，同時單片機P1.3和P1.4接到IC3A的輸入端，中斷源的識別由程序查詢來處理，中斷優先順序為先右後左。部分源程序如下：
receive1：push psw
push acc
clr ex1 ； 關外部中斷1
jnb p1.1, right ； P1.1引腳為0,轉至右測距電路中斷服務程序
jnb p1.2, left ； P1.2引腳為0,轉至左測距電路中斷服務程序
return： SETB EX1； 開外部中斷1
pop? acc
pop? psw
reti
right： ...? ； 右測距電路中斷服務程序入口
? ajmp? return
left： ... ； 左測距電路中斷服務程序入口
? ajmp? return
4、計算超聲波傳播時間
在啟動發射電路的同時啟動單片機內部的定時器T0，利用定時器的計數功能記錄超聲波發射的時間和收到反射波的時間。當收到超聲波反射波時，接收電路 輸出端產生一個負跳變，在INT0或INT1端產生一個中斷請求信號，單片機響應外部中斷請求，執行外部中斷服務子程序，讀取時間差，計算距離。其部分源程序如下：
RECEIVE0： PUSH PSW
PUSH ACC
CLR EX0 ； 關外部中斷0
? MOV R7, TH0 ； 讀取時間值
MOV R6, TL0?
CLR C
MOV A, R6
SUBB A, #0BBH； 計算時間差
MOV 31H, A ； 存儲結果
MOV A, R7
SUBB A, #3CH
MOV 30H, A?
SETB EX0 ； 開外部中斷0
POP ACC?
POP PSW
RETI
四、超聲波測距系統的軟體設計
軟體分為兩部分，主程序和中斷服務程序，如圖3（a）（b）(c) 所示。主程序完成初始化工作、各路超聲波發射和接收順序的控制。
定時中斷服務子程序完成三方向超聲波的輪流發射，外部中斷服務子程序主要完成時間值的讀取、距離計算、結果的輸出等工作。
五、結論
對所要求測量范圍30cm~200cm內的平面物體做了多次測量發現，其最大誤差為0.5cm，且重復性好。可見基於單片機設計的超聲波測距系統具有硬體結構簡單、工作可靠、測量誤差小等特點。因此，它不僅可用於移動機器人，還可用在其它檢測系統中。
思考：至於為什麼接收不用晶體管做放大電路呢，因為放大倍數搞不好，CX20106集成放大電路，還帶自動電平增益控制，放大倍數為76dB，中心頻率是38k到40k，剛好是超聲波感測器的諧振頻率
❷ 驅蚊器對小孩有害嗎
目前科學證明為寶寶最好的驅蚊工具就是蚊帳，同時電蚊拍也是不錯的選擇，花露水可以配合使用，其它的多少都會有一定危害！ 因為電蚊拍與孩子比較遠，是採用電壓技術，超聲波肯定對孩子有輻射！建議不要用！
❸ 超聲波和次聲波有什麼特性初中知識！
次聲波是頻率低於20赫茲的聲波。一般來說，人耳所能接受的聲波在20—20000赫茲之間，聲波頻率高於20000赫茲的，稱為超聲波；低於20赫茲的約則為次聲波。次聲波與超聲波一樣都看不見、聽不到、摸不著，但次聲波頻率低、波長長，所以傳播距離很遠。次聲波的另一個重要特性是有較強的穿透能力，既能穿透空氣、海水、土壤，也能穿透飛機機體、艦艇殼件、坦克車體，以及堅固的鋼筋混凝土構體。例如頻率為3.44赫茲的次聲波，其波長100米，能穿透建築物的堅固牆壁，當然，對於人體來說更是不在話下。
據報道，次聲波亡人的事件還真有不少。1980年，一艘名叫「馬爾波羅」的帆船在由紐西蘭駛往英國的途中突然神秘地失蹤；20年後，卻在火地島附近被人發現。船上的一切都原封不動、完好如初。就連已死多年的船員也都各就各位，保持著工作狀態。科學家對他們的神秘死亡引起了極大的關注，經過長期研究，終於發現，原來他們正是死於海上風暴產生的次聲。
1992年11月24日，桂林上空發生了一起空難，141人死亡，成為中國民航史上最慘烈的飛機失事事件。當事件的原因經多方解釋而未肯定之時，中國聲學研究所的專家，提出了存在著因「次聲波」的作用而致使飛機墜毀的可能性。桂林屬半丘陵地帶，氣團依山勢走向而上下浮動，引起氣流震動，會產生一種「山背波」的次聲波，當飛機遇到這種危害極大的由次聲波引起的晴空湍流時，如同落入一個風旋渦中，在擠壓力、沖力等多種強勁外力的作用下，將造成飛機失控、產生機毀人亡的惡果。最近研究結果表明，次聲波對飛機的影響還有一種「生物效應」。該理論認為，當次聲波的頻率接近人體頻率時，就有可能產生「共振」，飛機駕駛員無法承受這種強烈的效應，就有致命的危險。也就是說，此次空難的兇手很可能就是這種次聲波。
那麼，次聲波為何會造成人員不流血卻出現嚴重傷亡的現象呢?科學研究表明：人體的內臟，有其固有的振動頻率，而這種頻率也在0.01—20赫茲之間，也就是說，它和次聲波的頻率相似。這樣一來，當外來的次聲波不管是自然形成的，還是人為製造的，一旦它的振動頻率與人體內臟的振動頻率相同或接近時，就會引起各種臟器的共振，這一共振便會使人煩躁、耳鳴、頭痛、失眠、惡心、視覺模糊、吞咽困難、肝胃功能失調紊亂；嚴重時，還會使人四肢麻木、胸部有壓迫感。特別是與人的腹腔、胸腔和顱腔的固有振動頻率一致時，就會與內臟、大腦等產生共振，甚至危及性命。
次聲波這些神奇的功能：無聲無息地傳播，波長不易衰減，且易與自然界的次聲波混在一起，難以被人察覺等特點，早就引起軍事專家的高度注意。一些國家正在是利用次聲波的性質進行次聲波武器的研製。初步選定利用次聲波進行作戰的方向是次聲波發生器和次聲波炸彈